The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Additive manufacturing (AM) techniques rely on a layered approach to building a metal or plastic part or component from the bottom up. Also referred to as 3D printing, additive manufacturing can be used to create extremely complex parts very quickly. A high level example of an AM system is shown in FIG. 1 being used to form a part one layer at a time. A heat source is used to heat each layer, typically by raster scanning the heat source back and forth across sections of the layer. The heat source melts the powdered material forming the layer and then a subsequent layer of powdered material is laid down and heated. These operations are alternately repeated for the layers L1-L8 and the resulting finished part is thus made up of a plurality of layers, one melted on top of the previous one. Thus, a part made from the AM process is typically constructed of a large plurality of distinct layers of material.
With the AM process, however, material strength and hardness of the finished part may sometimes not be as high as one would like or need. In many instances parts made from the AM process will be somewhat fragile. This may lead to inadvertent damage of the part during subsequent handling, testing or other use of the AM produced part. The AM process is also limited by the ability of the heat source being used to melt the powdered material. As a result, parts made from the AM process usually are made from a single type of material.
Other technologies exist for peening or hardening various materials. For example, laser peening is the process of hardening or peening metal using a laser. Laser peening can impart a layer of residual compressive stress on a surface that is several times deeper than that attainable from conventional shot peening treatments. Short pulses of laser energy are focused and repositioned as needed during the laser peening process, and the process is repeated over the surface being worked on. The process may be repeated two or more times until a desired compression level is reached, thus producing a compressive layer of a desired depth in the material surface. Laser peening is highly effective in improving the fatigue resistance of metal parts.
High Velocity Laser Accelerated Deposition (HVLAD) technology for controlled laser-driven explosive bonding is a state-of-the-art proprietary methodology developed by Lawrence Livermore National Laboratory. This state-of-the-art process is enabled and facilitated by LLNL's high-performance solid-state laser technology. With HVLAD technology, a coating of a dissimilar material may be deposited on and bonded to a substrate. A high power laser pulse hits the film of deposited material covered by a thin water layer. The laser deposition on the water-material interface generates a large pressure accelerating film to velocities of a few hundred meters per second. The film hits the substrate at an oblique angle. The high velocity of impact induces the plastic flow of materials on the film-substrate interface. Shear flow, due to the oblique incidence, results in material mixing and extremely strong coating adhesion.
The HVLAD process uses powerful and high repetition rate production lasers for localized explosive bonding, thus producing a very broad range of advanced high-temperature and corrosion-resistant coatings with extreme interfacial bond strength. These interfacial bonds approach the ultimate tensile strength of the substrate. The deposition of protective metallic films and coatings on various metallic alloy, ceramic or composite substrates is important for many industrial applications. LLNL has now demonstrated that exceptionally high corrosion resistant and high wear resistant coatings can be deposited on a substrate material with exceptional interfacial bond strengths approaching the ultimate strengths of the underlying substrate materials. The HVLAD process may be conducted in a variety of manufacturing settings such as plants, aircraft hangers, ship yards, etc., under ambient conditions.
Accordingly, a need still exists to significantly improve the strength, hardness and other properties of parts made using the AM process by using one or more available technologies which, up to the present time, have not been integratable with the AM process.